The electron microscope is now an indispensable tool for studies in DNA metabolism. The instrument is useful for measurements of molecular size and conformation, for hybridization studies, for determination of DNA interaction with protein and for a variety of other procedures. The available methodologies are such that use of the instrument as an analytical tool should no longer be viewed as a special approach but rather as a routine and critical procedure in the same way that measurements of absorbancy or radioactivity are both routine and critical. This application is therefore a request to make available an instrument suitable for multi-user application so that facilities are available to a group of investigators at all times. The application details the work this group of investigators has already done using the electron microscope as well as that proposed. We also provide data on the instruments available on campus and indicate that none allows the ready access necessary.